Onboard Giotto, launched July 2 from West Germany, is a tiny monitoring device designed and partially built at the University of Florida's Space Astronomy Laboratory in Gainesville.

The 2-pound monitoring device, called Halley Optical Probe Experiment, will analyze the makeup and history of the comet by penetrating it. HOPE, financed by a $700,000 grant from NASA, will use a spectral photo polarimeter to examine Halley's individual wavelengths of light and determine the nature of its gases and ice.

Giotto, weighing 123 pounds, will slam into Halley's at midnight Greenwich mean time, March 13. Dust particles will bombard the tiny craft at 40 miles per second -- more than 100 times faster than a rifle bullet.

The satellite will be destroyed before passing through the comet, said Frank Govane, who co-designed HOPE with Jerry Weinberg, head of the Gainesville lab. The device will operate for only 15 minutes.

Before Giotto is obliterated, HOPE and more than 20 other devices will transmit data to a radio telescope at Parkes, New South Wales, Australia.

Giotto represents a chance for scientists to examine a comet in great detail. In the past, astronomers used the spectrum given off by a comet's light to guess its composition.

Every gas emits a unique spectrum -- a ''fingerprint'' -- from which scientists can determine which gas is present. However, spectra from celestial bodies are not always accurate, thus amplifying HOPE's significance.

Govane likened a comet's construction to that of an onion. Successive layers of a comet represent the evolution over time of the comet, like that of an onion, Govane said.

''To figure out what each layer contributes to the original product, you have to put together a model,'' Govane said. ''As you penetrate the 'onion,' you can see how it has changed over time.''